Flooding overshadows phosphorus availability in controlling the intensity of arbuscular mycorrhizal colonization in Sangyod Muang Phatthalung lowland indica rice

Abstract

Phosphorus (P) availability and soil water are two important environmental factors in lowland rice paddies. They limit the ability of rice to form mutualistic associations with arbuscular mycorrhizal fungi (AMF). The dynamics of this symbiotic interaction are intensified by phosphorus deficiency and attenuated by anaerobic conditions. However, the effects of combined phosphorus deficiency and anaerobic conditions on AMF symbiosis in paddy soil were unproven. The main objective of this study is to determine the influence of phosphorus and water availabilities on indigenous AMF colonization and community in Sangyod Muang Phatthalung (SMP) rice. Rice seedlings were grown in pots containing P-deficient organic paddy soil with or without phosphorus fertilization under non-flooded and flooded conditions for 2, 4 and 6 weeks. The application and omission of P soil fertilization influenced phosphate accumulations in rice seedlings, producing conditions of P-sufficiency and P-deficiency, respectively, in the plants. To determine the effects of phosphorus and water availabilities on AMF colonization and community structures, roots were analyzed microscopically and molecularly. Flooding considerably reduced the intensity of indigenous AMF root colonization whereas the non-enrichment of P availability did not. Reduced AMF colonization was concomitant with lower abundances of two major Glomeromycota ASVs in roots under flooding. This result suggested that soil water availability plays the primary role in shaping AMF communities in SMP roots. This study emphasized the primacy of water management when considering the use of AMF in the production of SMP rice in an organic cultivation system.